Massey Research Online - Browsing by Author "Knox JP"

Browsing by Author "Knox JP"

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Branched pectic galactan in phloem-sieve-element cell walls: Implications for cell mechanics
(American Society of Plant Biologists, 6/02/2018) Torode TA; O'Neill R; Marcus SE; Cornuault VRG; Pose S; Lauder RP; Kracun SK; Rydahl MG; Andersen MCF; Willats WGT; Braybrook SA; Townsend BJ; Clausen MH; Knox JP
A major question in plant biology concerns the specification and functional differentiation of cell types. This is in the context of constraints imposed by networks of cell walls that both adhere cells and contribute to the form and function of developing organs. Here, we report the identification of a glycan epitope that is specific to phloem sieve element cell walls in several systems. A monoclonal antibody, designated LM26, binds to the cell wall of phloem sieve elements in stems of Arabidopsis (Arabidopsis thaliana), Miscanthus x giganteus, and notably sugar beet (Beta vulgaris) roots where phloem identification is an important factor for the study of phloem unloading of Suc. Using microarrays of synthetic oligosaccharides, the LM26 epitope has been identified as a β-1,6-galactosyl substitution of β-1,4-galactan requiring more than three backbone residues for optimized recognition. This branched galactan structure has previously been identified in garlic (Allium sativum) bulbs in which the LM26 epitope is widespread throughout most cell walls including those of phloem cells. Garlic bulb cell wall material has been used to confirm the association of the LM26 epitope with cell wall pectic rhamnogalacturonan-I polysaccharides. In the phloem tissues of grass stems, the LM26 epitope has a complementary pattern to that of the LM5 linear β-1,4-galactan epitope, which is detected only in companion cell walls. Mechanical probing of transverse sections of M x giganteus stems and leaves by atomic force microscopy indicates that phloem sieve element cell walls have a lower indentation modulus (indicative of higher elasticity) than companion cell walls.
Comparative in situ analyses of cell wall matrix polysaccharide dynamics in developing rice and wheat grain
(Springer Verlag, 1/03/2015) Palmer R; Cornuault VRG; Marcus SE; Knox JP; Shewry PR; Tosi P
Cell wall polysaccharides of wheat and rice endosperm are an important source of dietary fibre. Monoclonal antibodies specific to cell wall polysaccharides were used to determine polysaccharide dynamics during the development of both wheat and rice grain. Wheat and rice grain present near synchronous developmental processes and significantly different endosperm cell wall compositions, allowing the localisation of these polysaccharides to be related to developmental changes. Arabinoxylan (AX) and mixed-linkage glucan (MLG) have analogous cellular locations in both species, with deposition of AX and MLG coinciding with the start of grain filling. A glucuronoxylan (GUX) epitope was detected in rice, but not wheat endosperm cell walls. Callose has been reported to be associated with the formation of cell wall outgrowths during endosperm cellularisation and xyloglucan is here shown to be a component of these anticlinal extensions, occurring transiently in both species. Pectic homogalacturonan (HG) was abundant in cell walls of maternal tissues of wheat and rice grain, but only detected in endosperm cell walls of rice in an unesterified HG form. A rhamnogalacturonan-I (RG-I) backbone epitope was observed to be temporally regulated in both species, detected in endosperm cell walls from 12 DAA in rice and 20 DAA in wheat grain. Detection of the LM5 galactan epitope showed a clear distinction between wheat and rice, being detected at the earliest stages of development in rice endosperm cell walls, but not detected in wheat endosperm cell walls, only in maternal tissues. In contrast, the LM6 arabinan epitope was detected in both species around 8 DAA and was transient in wheat grain, but persisted in rice until maturity.
Disentangling pectic homogalacturonan and rhamnogalacturonan-I polysaccharides: Evidence for sub-populations in fruit parenchyma systems.
(Elsevier, 25/04/2018) Cornuault VRG; Pose S; Knox JP
The matrix polysaccharides of plant cell walls are diverse and variable sets of polymers influencing cell wall, tissue and organ properties. Focusing on the relatively simple parenchyma tissues of four fruits – tomato, aubergine, strawberry and apple – we have dissected cell wall matrix polysaccharide contents using sequential solubilisation and antibody-based approaches with a focus on pectic homogalacturonan (HG) and rhamnogalacturonan-I (RG-I). Epitope detection in association with anion-exchange chromatography analysis indicates that in all cases solubilized polymers include spectra of HG molecules with unesterified regions that are separable from methylesterified HG domains. In highly soluble fractions, RG-I domains exist in both HG-associated and non-HG-associated forms. Soluble xyloglucan and pectin-associated xyloglucan components were detected in all fruits. Aubergine glycans contain abundant heteroxylan epitopes, some of which are associated with both pectin and xyloglucan. These profiles of polysaccharide heterogeneity provide a basis for future studies of more complex cell and tissue systems.
Extraction, texture analysis and polysaccharide epitope mapping data of sequential extracts of strawberry, apple, tomato and aubergine fruit parenchyma
(Elsevier, 1/04/2018) Cornuault VRG; Pose S; Knox JP
The data included in this article are related to the research article entitled “Disentangling pectic homogalacturonan and rhamnogalacturonan-I polysaccharides: evidence for sub-populations in fruit parenchyma systems” (Cornuault et al., 2018) [1]. Cell wall properties are an important contributor to fruit texture. These datasets compile textural and immunochemical analysis of polysaccharides of four economically important fruit crops: tomato, strawberry, aubergine and apple with contrasting textures and related taxonomical origins. Cell wall components and their extractability were assessed using characterized monoclonal antibodies. In addition, textural data obtained for the four parenchyma systems show variations in the mechanical properties. The two datasets are a basis to relate cell wall composition and organization to the mechanical properties of the fruit parenchyma tissues.
LM6-M: A high avidity rat monoclonal antibody to pectic α-1,5-L-arabinan
(10/07/2017) Cornuault VRG; Buffetto F; Marcus SE; Crepeau MJ; Guillon F; Ralet MC; Knox JP
1,5-arabinan is an abundant structural feature of side chains of pectic rhamnogalacturonan-I which is a matrix constituent of plant cell walls. The study of arabinan in cells and tissues is driven by putative roles for this polysaccharide in the generation of cell wall and organ mechanical properties. The biological function(s) of arabinan is still uncertain and high quality molecular tools are required to detect its occurrence and monitor its dynamics. Here we report a new rat monoclonal antibody, LM6-M, similar in specificity to the published rat monoclonal antibody LM6 (Willats et al. (1998) Carbohydrate Research 308: 149-152). LM6-M is of the IgM immunoglobulin class and has a higher avidity for α-1-5-L-arabinan than LM6. LM6-M displays high sensitivity in its detection of arabinan in in-vitro assays such as ELISA and epitope detection chromatography and in in-situ analyses.
Monoclonal antibodies indicate low-abundance links between heteroxylan and other glycans of plant cell walls
(Springer Verlag, 25/07/2015) Cornuault VRG; Buffetto F; Rydahl MG; Marcus SE; Torode TA; Xue J; Crepeau MJ; Faria-Blanc N; Willats WGT; Dupree P; Ralet MC; Knox JP
Plant cell walls are complex composites of structurally distinct glycans that are poorly understood in terms of both in muro inter-linkages and developmental functions. Monoclonal antibodies (MAbs) are versatile tools that can detect cell wall glycans with high sensitivity through the specific recognition of oligosaccharide structures. The isolation of two novel MAbs, LM27 and LM28, directed to heteroxylan, subsequent to immunisation with a potato cell wall fraction enriched in rhamnogalacturonan-I (RG-I) oligosaccharides, is described. LM27 binds strongly to heteroxylan preparations from grass cell walls and LM28 binds to a glucuronosyl-containing epitope widely present in heteroxylans. Evidence is presented suggesting that in potato tuber cell walls, some glucuronoxylan may be linked to pectic macromolecules. Evidence is also presented that suggests in oat spelt xylan both the LM27 and LM28 epitopes are linked to arabinogalactan-proteins as tracked by the LM2 arabinogalactan-protein epitope. This work extends knowledge of the potential occurrence of inter-glycan links within plant cell walls and describes molecular tools for the further analysis of such links.
Multi-scale spatial heterogeneity of pectic rhamnogalacturonan I (RG-I) structural features in tobacco seed endosperm cell walls
(Wiley, 3/09/2013) Lee KJD; Cornuault VRG; Manfield IW; Ralet MC; Knox JP
Plant cell walls are complex configurations of polysaccharides that fulfil a diversity of roles during plant growth and development. They also provide sets of biomaterials that are widely exploited in food, fibre and fuel applications. The pectic polysaccharides, which comprise approximately a third of primary cell walls, form complex supramolecular structures with distinct glycan domains. Rhamnogalacturonan I (RG-I) is a highly structurally heterogeneous branched glycan domain within the pectic supramolecule that contains rhamnogalacturonan, arabinan and galactan as structural elements. Heterogeneous RG-I polymers are implicated in generating the mechanical properties of cell walls during cell development and plant growth, but are poorly understood in architectural, biochemical and functional terms. Using specific monoclonal antibodies to the three major RG-I structural elements (arabinan, galactan and the rhamnogalacturonan backbone) for in situ analyses and chromatographic detection analyses, the relative occurrences of RG-I structures were studied within a single tissue: the tobacco seed endosperm. The analyses indicate that the features of the RG-I polymer display spatial heterogeneity at the level of the tissue and the level of single cell walls, and also heterogeneity at the biochemical level. This work has implications for understanding RG-I glycan complexity in the context of cell-wall architectures and in relation to cell-wall functions in cell and tissue development.
Sandwich enzyme-linked immunosorbent assay (ELISA) analysis of plant cell wall glycan connections
(20/04/2014) Cornuault VRG; Knox JP
Sandwich ELISA is a highly sensitive method that can be used to determine if two epitopes are part of the same macromolecule or supramolecular complex. In the case of plant cell wall glycans, it can reveal the existence of inter-polymers linkages, leading to better understanding of overall cell wall architectures. This development of a conventional sandwich ELISA protocol uses a carbohydrate-binding module (CBM), a small protein domain found in some carbohydrate catalysing or activating enzymes, and rat monoclonal antibodies (mAbs) which can be combined in the same ELISA plate without risk of cross reaction; the secondary anti-rat HRP antibody being only able to bind to the rat mAb and not the CBM. This protocol was developed and modified in the Prof. J. Paul Knox lab at the University of Leeds
The deconstruction of pectic rhamnogalacturonan I unmasks the occurrence of a novel arabinogalactan oligosaccharide epitope
(Oxford University Press (OUP), 1/11/2015) Buffetto F; Cornuault VRG; Rydahl MG; Ropartz D; Alvarado C; Echasserieau V; Le Gall S; Bouchet B; Tranquet O; Verhertbruggen Y; Willats WGT; Knox JP; Ralet MC; Guillon F
Rhamnogalacturonan I (RGI) is a pectic polysaccharide composed of a backbone of alternating rhamnose and galacturonic acid residues with side chains containing galactose and/or arabinose residues. The structure of these side chains and the degree of substitution of rhamnose residues are extremely variable and depend on species, organs, cell types and developmental stages. Deciphering RGI function requires extending the current set of monoclonal antibodies (mAbs) directed to this polymer. Here, we describe the generation of a new mAb that recognizes a heterogeneous subdomain of RGI. The mAb, INRA-AGI-1, was produced by immunization of mice with RGI oligosaccharides isolated from potato tubers. These oligomers consisted of highly branched RGI backbones substituted with short side chains. INRA-AGI-1 bound specifically to RGI isolated from galactan-rich cell walls and displayed no binding to other pectic domains. In order to identify its RGI-related epitope, potato RGI oligosaccharides were fractionated by anion-exchange chromatography. Antibody recognition was assessed for each chromatographic fraction. INRA-AGI-1 recognizes a linear chain of (1→4)-linked galactose and (1→5)-linked arabinose residues. By combining the use of INRA-AGI-1 with LM5, LM6 and INRA-RU1 mAbs and enzymatic pre-treatments, evidence is presented of spatial differences in RGI motif distribution within individual cell walls of potato tubers and carrot roots. These observations raise questions about the biosynthesis and assembly of pectin structural domains and their integration and remodeling in cell walls.

Browsing by Author "Knox JP"

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